Field of the Invention
The present subject matter is directed generally to joint replacement implants and, more particularly, to multi-axis ankle joint replacement implants.
Background Information
The concept of total ankle arthroplasty has a long and relatively unsuccessful history due to the high failure rate often associated with the original implant devices and implantation techniques. Only recently has total ankle arthroplasty regained some recognition as a viable treatment for limited indications and as a viable alternative to an ankle joint fusion, which is often referred to as the gold standard of treatment. It has been shown that replacement of an ankle joint with an ankle prosthesis can be particularly challenging due to the relatively small articular contact surfaces of the ankle, complex biomechanics of both the ankle and hindfoot joints, limited and risky access to the ankle joint during replacement, and wide variation in patient candidacy. Past flawed design rationale and the above factors have led to a high rate of post-operative complications such as loosening of the ankle prosthesis, subsidence, pain, abnormal ankle prosthesis wear, and/or meniscal/bearing breakdown—often leading to ankle implantation failure.
There are two types of ankle prosthetics for ankle arthroplasty or replacement that are generally available, a fixed bearing ankle prosthetic and a mobile bearing ankle prosthetic. Both types of ankle prosthetics utilize either a three (3) piece and two (2) component design (with the meniscal portion/bearing locking into the tibia plate) or a three (3) piece and three (3) component design (with a mobile/unlocked bearing) including an upper, middle, and lower component (tibia, bearing, and talus component, respectively). Once a particular type is chosen, it is difficult, if not impossible, to revise the surgery and provide another type of implant, particularly if the metal to bone interface(s) is/are not to be disturbed. As well, it is difficult, if not possible, to perform revision surgery on a mobile bearing ankle prosthetic in order to change the amount of translation freedom.
It is therefore apparent from the above that the need exists for an ankle joint replacement implant that allows interchangeability from and/or between a mobile bearing ankle joint replacement implant and a fixed bearing ankle joint replacement implant. It is also apparent from the above that the need exists for an ankle joint replacement implant that allows changeability from a mobile bearing ankle joint implant providing a particular degree of translation to a mobile bearing ankle joint implant providing a different degree of translation.